The present invention is directed to an impression packer and more particularly this invention is directed to an impression packer utilizing a mixture of partially cured synthetic nitrile rubber, natural rubber smoked sheet, silica powder and rubber processing oil rolled into sheet form for the impression receiving sleeve.
It is often very desirable to know the condition of pipe or liners located in wells. For example, it is important to know whether or not perforations or slots in a liner are open or plugged. It is also often important to know the condition of the pipe or liner itself, i.e., is it in good condition or is it cracked or split. It is also sometimes desirable to know what the surface of a formation penetrated by a well is like.
One means of determining the condition of these downhole occurrences is the use of an impression packer. An impression packer is a device which is run down hole and has a surface which is pressed against the pipe or formation which surface will form and retain an impression of irregularities in the surface of the pipe such as, for example, perforations or cracks in the pipe. Impression packers are not new. Such packers are disclosed in U.S. Pat. Nos. 2,416,441; 2,618,014; and 2,653,474, for example. However, impression packers known heretofore had only limited success. A principal cause of the lack of success is believed to be the absences of a suitable material for receiving and retaining the impression.
The present invention provides a material for forming an impression sleeve of an impression packer. The impression sleeve is formed of a material which will retain impressions and which will expand and retract so that an impression may be made and then so the packer may be removed from the well so the impression may be examined. The material used to form the impression sleeve must be smooth so that impression detail will be readily observable on the sleeve after a run of the impression packer. That is, the surface of the impression sleeve must not be so rough that detail of the impression is lost. Generally a surface which feels smooth to the hand and visually appears to have no major roughness is required.